Liquid Carbonyl Sulfide Research Articles

Fumigation trial on direct application of liquid carbonyl sulphide to wheat in a 2500 t concrete silo

Wheat (Australian Standard White) with a moisture content of 10.2% was fumigated with carbonyl sulphide (COS) at a calculated application rate of 24.14 g m −3, in a sealed concrete vertical silo (3512 m 3, 2500 t wheat) located at Nevertire, NSW, Australia. The COS was applied as a liquid via the top of the silo and released 2 m below the grain surface. The application of 84.5 kg of COS was completed within 30 min. With 2 h of recirculation using a 0.4 kW fan, the in-silo concentrations of COS achieved equilibrium with a concentration variation less than 5% of the mean. After a two-day exposure period, the COS concentration in the silo remained at 29 g m −3. The concentration×time product ( Ct) was then 1900 g h m −3, and this achieved complete kill of all life stages of mixed-age cultures of Sitophilus oryzae, Rhyzopertha dominica, Tribolium castaneum and Trogoderma variabile. After 2-days exposure, the silo was aired overnight with an aeration fan (25 kW) resulting in a COS in-silo concentration of below 4 ppm. This is 2.5 times lower than the Australian Experimental Threshold Limit Value (TLV) of 10 ppm. Residues of COS in the wheat declined to below the Australian Experimental Maximum Residue Limit (MRL) of 0.2 mg kg −1 after overnight aeration. The COS was not detected in any outloading samples at concentrations above the detection limit (0.05 mg kg −1). The workspace and environmental levels of COS were monitored during application, fumigation, aeration and outloading. The levels of COS and hydrogen sulphide (H 2S) were less than the detection limit of 0.1 ppm, which was 100 times lower than the TLV of 10 ppm. The treatment with COS had no affect on the wheat germination and seed colour when compared with untreated controls. Oil quality tests showed that COS had no effect on total lipid (made from treated wheat) content or the lipid colour.

How good is the second cumulant approximation to the reorientational correlation functions in liquid?

A general relation linking the angular velocity and reorientational correlation functions is known but it is only of formal character and low practical use. The second cumulant approximation for linear or symmetric top molecules simplifies the calculations to an extent which makes the problem accessible to mathematical analysis and physical interpretation. The question of the quality of this approximation becomes crucial in this context. We used the molecular dynamics (MD) simulations method to calculate both the angular velocity and reorientational correlation functions for liquid carbonyl sulphide (OCS). The relation between these correlation functions, predicted by the second cumulant approximation, was then carefully tested.

Many-body correlations in multipole-induced dipole absorption spectra of liquid OCS

Time correlation functions for several multipole-induced dipole moments corresponding to absorption in the far-infrared spectral region have been evaluated from molecular dynamics computer simulations of liquid carbonyl sulfide (OCS). Five state points along the liquid-vapor coexistence curve have been investigated. The dipole-, quadrupole- and octopole-induced dipole moments have been estimated for the interacting pairs of molecules in the liquid. The induced moments are produced by the action of the electric fields of the molecular electrostatic multipoles upon the anisotropic polarizabilities of the OCS. The component n-body ( n = 2,3,4) time correlation functions for these multipole-induced dipole moments as well as those for the cross-correlation functions between the induced and the permanent dipole moments of these molecules have been calculated. It is shown that the n-body terms involved in the time correlation functions containing quadrupole-induced dipole moments cancel each other at long times. Furthermore, 4-body correlations are significantly less important than the 2- and 3-body contributions for all induction mechanisms investigated here.

Vibrational dephasing in liquid carbonyl sulfide: comparison between molecular dynamics of rigid and flexible molecular models

Vibrational dephasing of the ν 1 and ν 3 stretching modes of carbonyl sulfide, OCS, was investigated by computer simulations of the liquid in the states corresponding to 183, 243 and 273 K. Perturbation theory plus simulation of rigid molecules result in vibrational correlation functions which disagree with experimental ones. Systematic changes to other intermolecular potential and anharmonicity constants proposed in the literature show that dephasing in this system is more sensitive to modifications in the inter than in the intramolecular potential. In order to investigate possible flaws of the perturbation theory/rigid molecules simulation method, molecular dynamics considering fully flexible OCS molecules was undertaken for the liquid at 273 K. Even then, the slow decay of the vibrational correlation function points to the effective intermolecular potential, and not to the approximations involved in the rigid simulation method, as responsible for disagreements with available experimental data. The calculated increasing of vibrational frequencies in the liquid as compared to the gas phase values is not confirmed by the experiments, and indicates that the effective Lennard-Jones potential proposed in the literature is too much repulsive in predicting vibrational frequency shifts in liquid OCS.

Molecular dynamics simulation of far infrared absorption in liquid OCS

The line shapes of the far infrared absorption spectra of liquid carbonyl sulfide were calculated by molecular dynamics simulation at the thermodynamic state of 298 K and a molar volume of 61.70 cm 3/mol. The corresponding time correlation functions of the system dipole moment were separated into contributions arising from the permanent molecular dipoles and from the interaction-induced dipole moments evaluated from a first-order multipole-induced dipole scheme considering the electrostatic multipoles up to the octupole moment. We conclude that the far infrared absorption spectrum of liquid carbonyl sulfide is strongly dominated by the orientational spectrum of the permanent dipoles at lower wavenumbers and, in addition, by the correlation of octupole-induced dipoles at high frequencies.

Time correlation functions of liquid OCS. A molecular dynamics simulation study

The single molecule dynamical properties of carbonyl sulfide at liquid densities were investigated as a function of temperature and the intermolecular potential model. The results show that electrostatic contributions of the dipole and quadrupole moment do not influence the dynamical properties proposed by the site—site “Lennard-Jones” model of this liquid. The satisfactory agreement between simulated and experimentally obtained reorientational correlation functions confirm that the Lennard-Jones potential describes the dynamics of the liquid accurately. The rotational dynamics of liquid carbonyl sulfide may be analysed by the “Gaussian” cage model for hindered reorientational motion.

Molecular dynamics investigations of the electrostatic interactions in liquid carbonyl sulphide

Molecular dynamics simulation was used to obtain information concerning the electrostatic contributions of dipole, quadrupole and octupole moments to the pair potential of liquid carbonyl sulphide. The influence of electrostatics is determined by the equilibrium properties of the liquid. These indicate that taking into account dipole and quadrupole moments, results are obtained in accordance with the Lennard-Jones model. Potential models including the octupole moment are shown to give a less adequate description of the liquid carbonyl sulphide.

Test of effective pair potential models by molecular dynamics simulation on liquid OCS

Molecular Dynamics simulation on liquid carbonyl sulphide has been used to develop a new effective atom-atom intermolecular potential in the form of a (12-6) Lennard-Jones equation. This model has been used to study thermodynamic properties. self-diffusion coefficients and intermolecular pair correlation functions at three thermodynamics states between 243 and 300 K.

ChemInform Abstract: TEMPERATURE STUDY OF RAYLEIGH AND RAMAN LINE SHAPES IN LIQUID CARBONYL SULFIDE

Chemischer InformationsdienstVolume 16, Issue 11 Physical Organic Chemistry ChemInform Abstract: TEMPERATURE STUDY OF RAYLEIGH AND RAMAN LINE SHAPES IN LIQUID CARBONYL SULFIDE B. HEGEMANN, B. HEGEMANNSearch for more papers by this authorJ. JONAS, J. JONASSearch for more papers by this author B. HEGEMANN, B. HEGEMANNSearch for more papers by this authorJ. JONAS, J. JONASSearch for more papers by this author First published: March 19, 1985 https://doi.org/10.1002/chin.198511051AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue11March 19, 1985 RelatedInformation

Temperature study of Rayleigh and Raman line shapes in liquid carbonyl sulfide

Temperature study of Rayleigh and Raman line shapes in liquid carbonyl sulfide

Reorientational motion, collision-induced scattering, and vibrational relaxation in liquid carbonyl sulfide

The rotational and vibrational behavior of neat liquid carbonyl sulfide under its own vapor pressure is investigated through Raman line shape studies of the symmetric ν1 C=S stretching mode over the temperature range T=183 to 303 K. The reorientational motion is found to be near the diffusional limit. Various methods of determining the reorientational correlation time τθ are compared and their validity discussed. The contribution of collision-induced scattering to the ν1 mode rotational line shape is examined semiquantitatively. It is found that the relative contribution of collision-induced scattering to the overall rotational line shape increases with increasing temperature and decreasing density, whereas the second moment of the collision-induced line shape decreases. Assuming the separability of the collision-induced scattering contribution and the reorientational contribution to the observed line shape, the experimental data are discussed qualitatively in terms of the dipole–induced–dipole (DID) theory of Balucani and Vallauri. The vibrational relaxation mechanism for the ν1 mode is attributed to dephasing and interpreted by Kubo line shape theory. The dephasing is found to be in the ‘‘motionally narrowed’’ regime and discussed qualitatively in terms of attractive dipolar forces.